ERα and ERβ Homodimers in the Same Cellular Context Regulate Distinct Transcriptomes and Functions

Area of Science:

• Endocrinology
• Molecular Biology
• Cancer Research

Background:

• Estrogen receptors ERα and ERβ are nuclear receptors that bind estrogen (E2) and regulate gene transcription.
• ERα is associated with breast cancer growth, while ERβ is generally considered anti-proliferative.
• Their distinct cellular functions are not fully understood due to differing cellular contexts.

Purpose of the Study:

• To dissect the similarities and differences between ERα and ERβ functions.
• To generate a novel cell model for direct comparison of ERα and ERβ homodimers in an identical cellular context.
• To investigate the distinct effects of ERα and ERβ on cell proliferation, migration, and gene expression.

Main Methods:

• Generated a novel breast cancer MCF7 cell model with Tet-Off-inducible ERβ expression and CRISPR-cas9 deletion of ERα.
• Utilized RNA sequencing to analyze gene expression changes regulated by E2 via ERα or ERβ.
• Performed functional gene ontology enrichment analysis and chromatin binding assays.

Main Results:

• ERα and ERβ regulate MCF7 cell proliferation in opposite directions: E2 increases proliferation via ERα but reduces it via ERβ (G2/M arrest).
• ERβ differentially impacts cell migration: increasing it in the absence of ligand but reducing it upon E2 treatment, while ERα has no significant effect.
• RNA sequencing identified distinct transcriptomes regulated by E2 via ERα (417 genes) and ERβ (503 genes), with ERβ specifically impacting extracellular matrix organization.

Conclusions:

• Within the same cellular context, ERα and ERβ exhibit opposing roles in cell proliferation and distinct effects on cell migration.
• Each estrogen receptor regulates a unique set of target genes in response to E2.
• The developed cell model is a valuable resource for further understanding the distinct mechanisms of ERα and ERβ isoforms.